Electric heating for hookah

ABSTRACT

Electric heat for generating smoke from tobacco or the like in a hookah type smoking pipe. Electric heat is obtained from an electrically powered heating element which may be placed proximate the tobacco. The heating element may be contained within a housing which in turn may be placed above the smoking chamber of the hookah. The housing may have adjustably damped holes disposed to pass air over the heating element. Electrical circuitry serving the heating element may comprise a step down transformer and a voltage adjusting switch. The heating element may be integral with the hookah, may take the form of a separate component which is mountable over the smoking chamber of the hookah, or may comprise a free standing assembly which may be placed to stand adjacent to the hookah.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation-in-Part of U.S. Non-Provisional application Ser. No. 12/393,286 filed Feb. 26, 2009, and claims the benefit of priority thereto.

FIELD OF THE INVENTION

The present invention relates to water pipes for smoking combusted materials, of the type known as hookahs, and more particularly to an electric heating source for hookah type smoking pipes.

BACKGROUND OF THE INVENTION

Hookah water pipes have long been used in smoking using combusted materials such as tobacco. As traditionally practiced, a hookah provides a water receptacle having an inlet conduit and at least one and often several outlet conduits. Smoke enters the water receptacle through the inlet conduit and is distributed to individual smokers through the outlet conduits, which are typically connected to hoses. Smoke is generated in a bowl in which a combustible substance such as tobacco is placed. A heat source is placed over the tobacco. In traditional practice, ignited charcoal may be used as the heat source.

Heating the tobacco generates smoke, which is drawn into the water receptacle through a supply conduit. The supply conduit is arranged to terminate below the level of the water within the water receptacle to assure filtration of raw smoke obtained from the bowl. The act of breathing air from the head space of the water receptacle induces partial vacuum in the head space, which in turn draws in smoke from the bowl through the supply conduit.

This arrangement requires that a fuel such as charcoal be provided and suitably ignited. This heat source must be maintained during smoking so that the combustible material is suitably roasted. It is possible for products of combustion, such as volatile gasses and ash to be conducted into the water receptacle along with smoke which intentionally generated by heating the tobacco or other combustible material.

It is difficult at best to regulate the output of a combustion based heat source. Also, smoke and other products of combustion may be objectionable within a closed room or building.

Use of electric heating sources has been proposed. There remain issues of control of heat output and limitation of potentially hazardous voltages in an electric heating source for a hookah style water pipe.

SUMMARY OF THE INVENTION

The present invention replaces combustion of fuel as the heat source in a hookah type water pipe in favor of electric heat. The electric power source and optional controller for the electric heater may take any one of several forms. In one form, the power source may be removably placed in the bowl or otherwise suspended from or supported on the hookah. A second form is to make the electric power source integral with the bowl or other part of the hookah. A third form is to provide the electric power source as a free standing assembly which is separate from the hookah, although operably disposed to heat a combustible such as tobacco and to conduct smoke from the heated combustible to the water receptacle of the hookah.

The electric supply may be controlled such that the wattage consumed is variable. Optionally, a thermostatic control may be provided to control wattage and heat output. In another option, a manual variable switch may be used to control wattage and heat output.

The heating element may comprise an exposed resistive element, or may comprise a covered resistive element, such as a light bulb.

Another heating control is regulation of air flowing past the heat source to tobacco or the like which is to be smoked. Regardless of the nature of the power supply and its controller, the electric heater may have a damper to control air flow through holes formed in the top of the heater and holes formed in the side of the heater.

It is an object of the invention to eliminate burning a fuel in a hookah as a heat source for roasting a combustible material such as tobacco.

Another object of the invention is to utilize electrical power at inherently safe voltages.

A further object of the invention is to control the amount of heat which is produced by an electric heater.

Still another object of the invention is to regulate air flow through the heater.

It is an object of the invention to provide improved elements and arrangements thereof by apparatus for the purposes described which is inexpensive, dependable, and fully effective in accomplishing its intended purposes.

These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Various objects, features, and attendant advantages of the present invention will become more fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views, and wherein:

FIG. 1 is a side view of a hookah using an electrical heat source for generating smoke according to at least one aspect of the invention.

FIG. 2 is a side view of a hookah using an electrical heat source according to at least a second aspect of the invention.

FIG. 3 is an enlarged detail view of an alternative to the component seen at the top of FIG. 1.

FIG. 4 is an enlarged detail view of an alternative to the component seen at the bottom of FIG. 2.

FIG. 5 is a side view of a hookah and a separate, free standing electric heater, according to a further aspect of the invention.

FIG. 6 is a perspective view of a heater which may be used with a hookah according to at least one aspect of the invention.

FIG. 7 is a top view of FIG. 6.

FIG. 8 is a perspective view of an alternative form of a heater such as the heater of FIG. 6.

FIG. 9 is a side cross sectional view of another heater which may be used with a hookah according to at least one aspect of the invention.

FIG. 10 is a side view of another heater which may be used with a hookah according to a further aspect of the invention, partially in section.

DETAILED DESCRIPTION

FIG. 1 shows a hookah type water pipe 100 having an electrical heat source for generating smoke. The hookah type water pipe 100 may comprise a conventional hookah 10 which comprises a liquid chamber 12, a smoking chamber 14 for receiving a combustible substance such as tobacco 16 and for generating smoke (not shown) by subjecting the tobacco 16 to heat. As employed herein, the term “chamber” will be understood to encompass both an enclosed space for performing a specified function and also surrounding structure such as walls, floor, etc., as may be necessary to define and maintain structural integrity of the enclosed space.

In conventional hookahs, heat is generated by placing charcoal (not shown) above or within the smoking chamber 14. The charcoal may be contained in a partially open cage (not shown) which is placed on the tobacco 16 or otherwise in heat exchange relation thereto. The charcoal is ignited. Heat from the burning charcoal is exposed to the tobacco 16. The tobacco 16 is partially combusted, thereby generating smoke. As employed herein, the term “heat exchange relation” will be understood to define any location in which an electric heater may expose a combustible substance to enough heat that the combustible substance partially combusts, thereby generating smoke (for example, in direct contact with, separated by a barrier, above, or below the combustible substance).

Smoke is drawn through a smoke supply conduit 18 disposed to conduct gasses and smoke from the smoking chamber 14 to the liquid chamber 12. Smoke is discharged into the liquid chamber by partial vacuum induced when a person (not shown) using the hookah 10 inhales through a smoking conduit 20 disposed to conduct cooled gasses and smoke from the smoking chamber 12 to the person smoking using the hookah 10. A hookah such as the hookah 10 may have more than one smoking conduit 20, including for example the smoking conduit 22. This enables the hookah 10 to be used for smoking simultaneously by more than one person. The smoking conduits 20, 22 may comprise flexible hoses.

It will be seen in FIG. 1 that the liquid chamber 12 is partially filled with water W. The water W is sufficient in volume to cover the lower open end 24 of the smoke supply conduit 18. When a person inhales through a smoking conduit 20 or 22, a partial vacuum is induced in the headspace H of the liquid chamber 12. Smoke and gasses such as air drawn from the smoking chamber 14 pass through the water W and are cooled thereby prior to passing to the headspace H. Inhalation continues until the person inhales cooled smoke from the headspace H. Vacuum levels within the liquid chamber 12 may be moderated by an air valve 26 which incorporates a check valve (not separately shown) adapted to allow air to pass from the exterior of the hookah 10 to the headspace H. The unidirectional nature of the check valve prevents smoke and gasses from exiting the liquid chamber 12 through the air valve 26.

The smoking conduits 20, 22, the conduit 28 serving the air valve 26, and the smoke supply conduit 18 pass through a gasket 30 which is arranged to close the top of the liquid chamber 12 and to pass the smoke supply conduit 17, the conduit 28, and each one of the smoking conduits 20, 22 from the liquid chamber 12 to the exterior thereof while sealing the smoking chamber 12 against loss of smoke residing therein.

In a traditional hookah such as the hookah 10, a plate 32 projects or radiates outwardly from the smoke supply conduit 18 between the smoking chamber 14 and the gasket 30. Also in a traditional hookah such as the hookah 10, the tobacco 16 is contained in a bowl 34, which bowl 34 may serve as the lower portion of the smoking chamber 14. The upper portion of the smoking chamber 14 may have a covering member (not shown), may comprise the previously mentioned cage for containing burning charcoal, or may be open to the atmosphere.

It should be noted at this point that orientational terms such as upper and lower refer to the orientations depicted in the referenced drawing figures. In turn, the drawing figures depict their subject matter in orientations of normal use, such as supported on a horizontal tabletop or desktop. Therefore, orientational terms must be understood to provide semantic basis for purposes of description, and do not limit the invention or its component parts in any particular way.

To further characterize conventional configuration of traditional combustion based hookahs, when the hookah type water pipe 100 is in an operable position resting on a generally horizontal supporting environmental surface, as shown in FIG. 1, the liquid chamber 12 is the lowermost component and the smoking chamber 14 is located above the liquid chamber 12 in vertical registry therewith. Also, the liquid chamber, 12, the gasket 30, the smoke supply conduit 18, and the smoking chamber 14 are generally coaxial and disposed in vertical registry with one another.

An electric heater 36 may be disposed in heat exchange relation to the smoking chamber 14. The electric heater 36 may comprise an electric supply circuit (not shown in its entirety, but seen in the view of FIG. 1 to include a supply conductor 38 and an electrical resistive heating element 40 which is connected to the supply conductor 38). As employed herein, the terms “circuit” and “circuitry” will be understood to encompass all conductors, components, and connections necessary to accomplish the described functions regardless of whether all such conductors, components, and connections are explicitly shown or described. Similarly, conductors shown or described in the singular will be understood to comprise more than one conductor where necessary to make function operational.

The electric supply circuit may be disposed to obtain electrical power at a first voltage and to supply electrical power to the resistive heating element 40 at a second reduced voltage, as will be further explained hereinafter.

The electric heater 36 may comprise a support element which holds the heating element 40 at a predetermined constant orientation relative to the smoking chamber 14 when the user is smoking, and a mounting element disposed to mount the support element and the heating element 40 to the smoking chamber 14. The mounting element may enable manual removal of the support element and the heating element 40 from the smoking chamber.

In FIG. 1, the support element may be that part of the housing 42 which grips the heating element 40. The mounting element may be that part of the housing 42 comprising a depending skirt 44 which, when the electric heater 36 is lowered into engagement with the bowl 34, is retained by gravity or by friction or by both.

FIG. 2 shows a hookah type water pipe 200 wherein structure corresponding to the electric heater 36 is integral with the smoking chamber 214. The smoking chamber 214 may be the structural and functional equivalent of the smoking chamber 14 of FIG. 1. The same holds true for smoking conduits 220, 222, an air valve 226, and a gasket 230.

The smoking chamber 214 provides a place to hold a combustible substance such as tobacco 16. An electric heating element 240 is held to the upper wall of the smoking chamber 214 such that heat radiated therefrom impinges upon the tobacco 16. The side wall of the smoking chamber 214 may have openings 246 for passage of air into the smoking chamber 214.

The hookah type water pipe 200 may comprise a base comprising an electrical chamber 248 for containing a voltage adjuster such as a step down transformer 250 and a plug and cord assembly 252 which is connected to the transformer 250 and which projects from the electrical chamber 248 so as to reach a standard 120 volt electrical receptacle (not shown) of a building (not shown). The circuitry which connects the plug and cord assembly 252 to the electric heating element 240, not shown in its entirety, thereby supplies electrical power to the electrical heating element 240 at reduced power from the 120 volt source. The circuitry may include a switch 254.

Voltage reduced from that of conventional 120 volts may be derived not only by use of the transformer 250. For example, a hookah such as the hookah 200 may comprise instead a conventional battery charger (not shown) which in addition to rectifying household AC power to DC power, also reduces the voltage. Reduced voltage may be obtained by incorporating a voltage divider (not shown) into the circuitry, by introducing resistors (not shown) into the circuitry, or in any other suitable way.

Referring momentarily to FIG. 3, the voltage adjuster contained within the electrical chamber 248 may comprise a conventional dimming switch 350 which is adjusted by a dial operator 354.

FIG. 4 shows an arrangement wherein a heating element may comprise one or more incandescent lamps 440A, 440B. Incandescent lamps 440A, 440B may be fabricated from materials which withstand fair high temperatures, so that despite their usual usage as light sources, the incandescent lamps 440A, 440B may be employed as heat sources. The housing 442 of the heater 436 may be ceramic and may house those portions of electrical supply circuitry which is omitted from view in FIG. 4. The heater 436 may in other ways be the structural and functional equivalent of the heater 36 of FIG. 1, for example.

Turning now to FIG. 5, a hookah type water pipe arrangement includes a hookah 500 which may be for example similar to the hookah 10. The hookah 500 may be a free standing assembly which is served by an electric heater 536 comprising a free standing base 502, a rigid generally vertical post 504 disposed to project upwardly from the base 502 when the base 502 is placed on a generally horizontal supporting environmental surface (not shown), and an electrical conductor 506 which projects from the vertical post 504 and extends to a heater head. The electrical conductor 506 may be flexible. The heater head comprises a housing 542 which encloses a heating element 540. The electrical conductor 506 is part of a circuit which is disposed to conduct electrical power to the heating element 540, and to enable the heater head to be placed over the smoking chamber 514 of the hookah 500 while the base 502 of the heater 536 rests on the generally horizontal supporting environmental surface beside the hookah 500. This is similar to how the heater 36 of FIG. 1 is placed over the smoking chamber 14 of its respective hookah 10. It will be seen that the electrical conductor 506 projects from the vertical post 504 at a height about equal to that of the smoking chamber 514, whereby length of the electrical conductor 506 is minimized while enabling operation when the hookah 500 and the electric heater 536 are placed on the same generally horizontal supporting environmental surface.

Referring now to FIGS. 6 and 7, a heater for a hookah type water pipe, such as the heater 36, may comprise a selectively variable damper arrangement disposed to regulate volume of air flow over the heating element, such as the heating element 40. A heater 636 may comprise a housing 642 which further comprises a top wall 643 and a perforated closure 645 having a top wall 655. The top wall 643 may have one or more openings 647 (concealed in FIG. 6, but shown in FIG. 7). The top wall 655 of the closure 645 may have corresponding openings 649. The closure is movably mounted on the tope wall 643, being rotatable about an axis A in FIG. 6 when grasped and manipulated by a projecting handle 651. As the closure 645 is rotated, the openings 649 come into registry with and move out of registry with the openings 647 of the top wall 643. The openings 647 and 649 are disposed to communicate between the electrical heating element and the exterior of the heater housing 642, thereby enabling air to pass over the electrical heating element. This arrangement of adjustably positioned overlying openings selectively damps or throttles air flow into the heater 636 and over the heating element (not shown) by varying the effective area of the holes 647 and 649 which overlie one another. Of course, the holes 647 and 649 may be moved entirely out of registry to close the holes 647 and 649 to air flow.

The heater 636 may be similar to the heater 36 of FIG. 1, having supporting structure (not shown in FIGS. 6 and 7) and electrical circuitry serving the electric heating element (not shown in FIGS. 6 and 7). This circuitry may include any of the features of the circuitry described with respect to the previously presented drawing figures and their respective subject matter. The housing 642 may partially envelop the electrical heating element in that the heating element may be covered at the top and at the sides, as depicted for the heater 36 in FIG. 1. The heating element is left uncovered at the bottom so that heat emanating from the heating element will heat combustible substances such as tobacco 16 which has been placed in the smoking chamber of the associated hookah, such as the hookah 10 of FIG. 1. The heater 636 may have a depending skirt 644 which serves to retain the heater on the bowl or corresponding structure of an associated hookah such as the hookah 10 when the heater 636 is mounted on the associated hookah.

FIG. 8 shows a heater 736 which is similar in function to the heater 636. However, in the heater 736, air passage openings 747 and 749 are formed on the respective side walls 755 and 753 of the heater housing 742 and the adjustable closure 745. The closure 745 may be rotatable about an axis A by grasping and manipulating a projecting handle 751.

A heater such as the heaters 636 and 736 may have air passage openings formed on both side walls such as the side walls 753 and 755 and also on the top walls such as the top walls 643 and 655 if desired.

FIG. 9 shows a heater position adjustment feature which may be introduced to a heater such as the heater 36. The heater adjustment feature may selectively vary proximity of the heating element from the floor of the smoking chamber, with the effect of varying proximity of a combustible substance such as tobacco 16 to the heating element of the heater.

A heater 836 may comprise an upper member 860 and a lower member 862 which slidably interfit. The lower member 862 may have a side wall 864 and a depending skirt 844. The depending skirt may be dimensioned and configured to cooperate with the bowl or smoking chamber of an associated hookah, such as the hookah 10 of FIG. 1. The lower member 862 may have a shoulder 866 which limits vertical motion of the upper member 860 by interference.

The upper member 860 may comprise a top wall 843 to which is mounted a heating element 840. A side wall 868 may be dimensioned and configured to fit closely to the side wall 864 of the lower member 862. The side walls may have dimensions and surfaces arranged such that friction between the outer surface 870 of the side wall 868 and the inner surface 872 of the side wall 864 will resist spontaneous or unintended movement therebetween, while still enabling manual force to reposition the upper member 860 and the lower member 864 as desired. Such adjustment, indicated by an arrow B in FIG. 9, varies proximity of the heating element 840 to for example tobacco 16 contained within the smoking chamber of a hookah to which the heater 836 has been mounted. The tobacco 16 is shown representatively, and may be supported in the position shown in FIG. 9 but not by the heater 836. For example, the tobacco 16 may be supported by the floor of a bowl, such as the bowl 34 of FIG. 1, of the hookah, or may be contained in a cage (not shown) supported by the bowl.

FIG. 10 shows a ceramic heater 936 which may be seen as a direct replacement for the charcoal which is traditionally used in conventional hookahs. The ceramic heater 936 may be contained in a partially open cage above or within the smoking chamber, similar to the smoking chamber 14 of FIG. 1. The ceramic heater 936 may be placed either directly on the tobacco or otherwise in heat exchange relation thereto.

The ceramic heater 936 may be similar to the one manufactured by Hotwatt, Inc., and constructed in like fashion. The ceramic heater 936 may comprise a ceramic body 901, terminated at both ends by the ceramic end seals 904. The ceramic heater 936 may encase a resistance wire element 902, packed within a heating element 903, such as magnesium oxide, that effectively converts the electricity received through the wire element 902 into heat. Either end seal 904 of the ceramic heater 936 may be terminated with flexible insulated lead wires 905. The flexible insulated lead wires 905 may lead into a voltage adjuster, similar to the voltage adjuster shown in FIG. 3, and may ultimately terminate with a plug and cord assembly, such as the plug and cord assembly 252 of FIG. 3.

While the ceramic heater may utilize a simple plug and cord assembly to be plugged directly into a traditional 120 volt outlet, the voltage adjuster will provide means for a user to vary and control the heat output of the ceramic heater 936 at the user's impulse. The circuitry of the ceramic heater 936 and voltage adjuster may include any of the features of the circuitry described with respect to the previously presented drawings and figures and their respective subject matter. It should be appreciated that the ceramic heater 936 may be used in conjunction with the selectively variable damper arrangement, such as the arrangement shown in FIGS. 6 and 7.

The present invention is susceptible to modifications and variations which may be introduced thereto without departing from the inventive concepts. For example, although the invention has been described as obtaining electrical power using cord and plug assemblies such as the cord and plug assembly 252, it would be possible to provide electrical storage devices such as an electrochemical cell, a battery of such cells, a capacitor, a super capacitor, an electric double layer capacitor, or any combination of these devices.

While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is to be understood that the present invention is not to be limited to the disclosed arrangements, but is intended to cover various arrangements which are included within the spirit and scope of the broadest possible interpretation of the appended claims so as to encompass all modifications and equivalent arrangements which are possible. 

1. A hookah type water pipe having an electrical heat source for generating smoke, comprising: a hookah comprising a liquid chamber, a smoking chamber for receiving a combustible substance and generating smoke by subjecting the combustible substance to heat, a smoke supply conduit disposed to conduct gasses from the smoking chamber to the liquid chamber, at least one smoking conduit disposed to conduct cooled gasses from the smoking chamber to a person smoking using the hookah type water pipe; and an electric heater disposed in heat exchange relation to the smoking chamber, comprising an electric supply circuit and an electrical resistive heating element connected to the electric supply circuit, wherein the electric supply circuit is disposed to obtain electrical power at a first voltage and to supply electrical power to the resistive heating element at a second reduced voltage.
 2. The hookah type water pipe of claim 1, wherein the electric heater is integral with the smoking chamber.
 3. The hookah type water pipe of claim 1, wherein the electric heater comprises a support element disposed to hold the heating element at a predetermined constant orientation relative to the smoking chamber, and a mounting element disposed to mount the support element and the heating element to the smoking chamber and to enable manual removal of the support element and the heating element from the smoking chamber.
 4. The hookah type water pipe of claim 1, wherein the hookah is a free standing assembly and the electric heater is a second free standing assembly having a base, a rigid generally vertical post disposed to project upwardly from the base when the base is placed on a generally horizontal supporting environmental surface, and an electrical conductor which projects from the vertical post and extends to the heater so as to conduct electrical power to the heater and to enable the heater to be placed over the smoking chamber while the base of the heater rests on the generally horizontal supporting environmental surface beside the hookah.
 5. The hookah type water pipe of claim 4, wherein the electrical conductor projects from the vertical post at a height about equal to that of the smoking chamber, whereby length of the electrical conductor is minimized while enabling operation when the hookah and the electric heater are placed on the same generally horizontal supporting environmental surface.
 6. The hookah type water pipe of claim 1, wherein the electric supply circuit comprises a voltage adjuster.
 7. The hookah type water pipe of claim 6, wherein the voltage adjuster comprises a step down transformer located within the base and a plug and cord assembly connected to the transformer, whereby electrical power at one hundred twenty volts may be obtained from an electrical receptacle, and electrical power at reduced voltage is supplied to the heating element.
 8. The hookah type water pipe of claim 6, wherein the voltage adjuster comprises a dimming switch.
 9. The hookah type water pipe of claim 1, further comprising a selectively variable damper arrangement disposed to regulate volume of air flow over the heating element.
 10. The hookah type water pipe of claim 1, further comprising a heater position adjuster disposed to selectively vary proximity of the heating element from the floor of the smoking chamber.
 11. The hookah type water pipe of claim 1, wherein the heating element comprises an incandescent light bulb.
 12. The hookah type water pipe of claim 1, wherein, when the hookah type water pipe is in an operable position resting on a generally horizontal supporting environmental surface, the liquid chamber is the lowermost component and the smoking chamber is located above the liquid chamber in vertical registry therewith; the hookah type water pipe further comprises a gasket disposed to close the top of the liquid chamber and to pass the smoke supply conduit and each one of the at least one smoking conduit from the liquid chamber to the exterior thereof while sealing the smoking chamber against loss of smoke residing therein; and the liquid chamber, the gasket, the smoke supply conduit, and the smoking chamber are generally coaxial and disposed in vertical registry with one another, whereby the hookah type water pipe displays conventional configuration of traditional combustion based hookahs.
 13. The hookah type smoking pipe of claim 12, further comprising a plate which further comprises a flange radiating outwardly between the smoking chamber and the gasket.
 14. The hookah type smoking pipe of claim 1, wherein the smoking conduit comprises a flexible hose.
 15. The hookah type smoking pipe of claim 1, wherein the heating element comprises a ceramic heater.
 16. An electric heater for a hookah type smoking pipe having a smoking chamber for receiving a combustible substance and subjecting the combustible substance to heat to generate smoke for smoking, comprising: an electrical heating element and an electric supply circuit disposed to conduct electrical power to the electrical heating element; a heater housing disposed to partially envelop the electrical heating element, having a plurality of holes formed therein and disposed to communicate between the electrical heating element and the exterior of the heater housing, for passing air over the electrical heating element, and an adjustable damper arrangement disposed selectively to vary the area of the plurality of holes and to close the holes; and a heater support element for holding the heater housing in a predetermined position relative to the smoking chamber wherein heat generated by the electric resistive heating element can impinge upon the combustible substance which has been placed in the smoking chamber.
 17. The electric heater of claim 16, wherein the housing has a top wall, and some of the holes are located on the top wall.
 18. The electric heater of claim 16, wherein the housing has a side wall, and some of the holes are located on the side wall.
 19. The electric heater of claim 18, wherein the housing has a top wall, and some of the holes are located on the top wall.
 20. The electric heater of claim 16, wherein the electrical supply circuit comprises a voltage adjuster. 